In Britain and Ireland there may be other species incorrectly identified as histrio. The abdomen is reddish brown above and darkened basally and apically. At least tergite eight spotted black.
In the female the sawsheath is blackened at least apically. The head is variable. In pale specimens, the head is yellow to red-brown marked with black around the ocelli and deprerssed areas of the face and off-white on the lower face. In dark females the head is mostly black above but with the lower face yellow-white. The thorax varies from yellow to red-brown or mostly black-brown. The mesonotum varies from having three black vertical stripes to being completely black. The legs are yellow-brown, blackened extensively in dark individuals.
In the male the head is black above and laterally behind the eyes more or less yellow-brown. The lower face is yellow-white. The thorax is black, except for the yellowish pronotal angles. The tibiae and tarsi of the hind legs are dark.
Euura histrio larvae thought to feed on white willow, crack willow and grey willow, though there may be doubt due to misidentification. On the continent the food plants are eared willow, goat willow and grey willow.
Size: Female: 8.2 - 9.3mm, male: 6.8 - 8.0mm.
Distribution: England, Scotland, Ireland
Flight period: March to May
Plant associations: Salix alba, Salix fragilis and Salix atrocinerea (white willow, crack willow and grey willow)
Benson, R.B., 1952. Handbooks for the Identification of British Insects. Hymenoptera, Symphyta, Vol 6, Section 2(a-c), Royal Entomological Society, London
Liston A, Knight G, Sheppard D, Broad G, Livermore L (2014) Checklist of British and Irish Hymenoptera - Sawflies, ‘Symphyta’. Biodiversity Data Journal 2: e1168. https://doi.org/10.3897/BDJ.2.e1168
Prous, M., Liston, A., Kramp, K., Savina, H., Vårdal, H. and Taeger, A., 2019. The West Palaearctic genera of Nematinae (Hymenoptera, Tenthredinidae). ZooKeys, 875, p.63-127
Schmidt, S., 1997. Amauronematus Konow, 1890-Ökologie und Taxonomie der nordeuropäischen Arten des fallax-Komplexes (Hymenoptera, Tenthredinidae). Beiträge zur Entomologie= Contributions to Entomology, 47(2), pp.227-326.